[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.20 by root, Sat May 10 22:30:28 2008 UTC vs.
Revision 1.29 by root, Tue Jul 29 10:20:33 2008 UTC

     loops
 SYNOPSIS
        use AnyEvent;
-       my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {
+       my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ...  });
-          ...
-       });
-       my $w = AnyEvent->timer (after => $seconds, cb => sub {
+       my $w = AnyEvent->timer (after => $seconds, cb => sub { ...  });
+       my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
+       print AnyEvent->now;  # prints current event loop time
+       print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
+       my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
+       my $w = AnyEvent->child (pid => $pid, cb => sub {
+          my ($pid, $status) = @_;
           ...
        });
        my $w = AnyEvent->condvar; # stores whether a condition was flagged
        $w->send; # wake up current and all future recv's
        $w->recv; # enters "main loop" till $condvar gets ->send
+       # use a condvar in callback mode:
+       $w->cb (sub { $_[0]->recv });
+INTRODUCTION/TUTORIAL
+    This manpage is mainly a reference manual. If you are interested in a
+    tutorial or some gentle introduction, have a look at the AnyEvent::Intro
+    manpage.
 WHY YOU SHOULD USE THIS MODULE (OR NOT)
     Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
     nowadays. So what is different about AnyEvent?
     Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of
     policy* and AnyEvent is *small and efficient*.
     First and foremost, *AnyEvent is not an event model* itself, it only
-    interfaces to whatever event model the main program happens to use in a
+    interfaces to whatever event model the main program happens to use, in a
     pragmatic way. For event models and certain classes of immortals alike,
     the statement "there can only be one" is a bitter reality: In general,
     only one event loop can be active at the same time in a process.
-    AnyEvent helps hiding the differences between those event loops.
+    AnyEvent cannot change this, but it can hide the differences between
+    those event loops.
     The goal of AnyEvent is to offer module authors the ability to do event
     programming (waiting for I/O or timer events) without subscribing to a
     religion, a way of living, and most importantly: without forcing your
     module users into the same thing by forcing them to use the same event
     model you use.
     For modules like POE or IO::Async (which is a total misnomer as it is
     actually doing all I/O *synchronously*...), using them in your module is
     like joining a cult: After you joined, you are dependent on them and you
-    cannot use anything else, as it is simply incompatible to everything
+    cannot use anything else, as they are simply incompatible to everything
-    that isn't itself. What's worse, all the potential users of your module
+    that isn't them. What's worse, all the potential users of your module
     are *also* forced to use the same event loop you use.
     AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
     fine. AnyEvent + Tk works fine etc. etc. but none of these work together
-    with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your
+    with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your
     module uses one of those, every user of your module has to use it, too.
     But if your module uses AnyEvent, it works transparently with all event
-    models it supports (including stuff like POE and IO::Async, as long as
+    models it supports (including stuff like IO::Async, as long as those use
-    those use one of the supported event loops. It is trivial to add new
+    one of the supported event loops. It is trivial to add new event loops
-    event loops to AnyEvent, too, so it is future-proof).
+    to AnyEvent, too, so it is future-proof).
     In addition to being free of having to use *the one and only true event
     model*, AnyEvent also is free of bloat and policy: with POE or similar
-    modules, you get an enourmous amount of code and strict rules you have
+    modules, you get an enormous amount of code and strict rules you have to
-    to follow. AnyEvent, on the other hand, is lean and up to the point, by
+    follow. AnyEvent, on the other hand, is lean and up to the point, by
     only offering the functionality that is necessary, in as thin as a
     wrapper as technically possible.
+    Of course, AnyEvent comes with a big (and fully optional!) toolbox of
+    useful functionality, such as an asynchronous DNS resolver, 100%
+    non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
+    such as Windows) and lots of real-world knowledge and workarounds for
+    platform bugs and differences.
-    Of course, if you want lots of policy (this can arguably be somewhat
+    Now, if you *do want* lots of policy (this can arguably be somewhat
     useful) and you want to force your users to use the one and only event
     model, you should *not* use this module.
 DESCRIPTION
     AnyEvent provides an identical interface to multiple event loops. This
     starts using it, all bets are off. Maybe you should tell their authors
     to use AnyEvent so their modules work together with others seamlessly...
     The pure-perl implementation of AnyEvent is called
     "AnyEvent::Impl::Perl". Like other event modules you can load it
-    explicitly.
+    explicitly and enjoy the high availability of that event loop :)
 WATCHERS
     AnyEvent has the central concept of a *watcher*, which is an object that
     stores relevant data for each kind of event you are waiting for, such as
-    the callback to call, the filehandle to watch, etc.
+    the callback to call, the file handle to watch, etc.
     These watchers are normal Perl objects with normal Perl lifetime. After
     creating a watcher it will immediately "watch" for events and invoke the
     callback when the event occurs (of course, only when the event model is
     in control).
     Many watchers either are used with "recursion" (repeating timers for
     example), or need to refer to their watcher object in other ways.
     An any way to achieve that is this pattern:
-      my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
+       my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
-         # you can use $w here, for example to undef it
+          # you can use $w here, for example to undef it
-         undef $w;
+          undef $w;
-      });
+       });
     Note that "my $w; $w =" combination. This is necessary because in Perl,
     my variables are only visible after the statement in which they are
     declared.
   I/O WATCHERS
     You can create an I/O watcher by calling the "AnyEvent->io" method with
     the following mandatory key-value pairs as arguments:
-    "fh" the Perl *file handle* (*not* file descriptor) to watch for events.
+    "fh" the Perl *file handle* (*not* file descriptor) to watch for events
+    (AnyEvent might or might not keep a reference to this file handle).
     "poll" must be a string that is either "r" or "w", which creates a
     watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
     is the callback to invoke each time the file handle becomes ready.
     Although the callback might get passed parameters, their value and
     Some event loops issue spurious readyness notifications, so you should
     always use non-blocking calls when reading/writing from/to your file
     handles.
-    Example:
-       # wait for readability of STDIN, then read a line and disable the watcher
+    Example: wait for readability of STDIN, then read a line and disable the
+    watcher.
        my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
           chomp (my $input = <STDIN>);
           warn "read: $input\n";
           undef $w;
        });
     Although the callback might get passed parameters, their value and
     presence is undefined and you cannot rely on them. Portable AnyEvent
     callbacks cannot use arguments passed to time watcher callbacks.
-    The timer callback will be invoked at most once: if you want a repeating
+    The callback will normally be invoked once only. If you specify another
-    timer you have to create a new watcher (this is a limitation by both Tk
+    parameter, "interval", as a strictly positive number (> 0), then the
-    and Glib).
+    callback will be invoked regularly at that interval (in fractional
+    seconds) after the first invocation. If "interval" is specified with a
+    false value, then it is treated as if it were missing.
-    Example:
+    The callback will be rescheduled before invoking the callback, but no
+    attempt is done to avoid timer drift in most backends, so the interval
+    is only approximate.
-       # fire an event after 7.7 seconds
+    Example: fire an event after 7.7 seconds.
        my $w = AnyEvent->timer (after => 7.7, cb => sub {
           warn "timeout\n";
        });
        # to cancel the timer:
        undef $w;
-    Example 2:
-       # fire an event after 0.5 seconds, then roughly every second
+    Example 2: fire an event after 0.5 seconds, then roughly every second.
-       my $w;
-       my $cb = sub {
-          # cancel the old timer while creating a new one
-          $w = AnyEvent->timer (after => 1, cb => $cb);
+       my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
+          warn "timeout\n";
        };
-       # start the "loop" by creating the first watcher
-       $w = AnyEvent->timer (after => 0.5, cb => $cb);
    TIMING ISSUES
     There are two ways to handle timers: based on real time (relative, "fire
     in 10 seconds") and based on wallclock time (absolute, "fire at 12
     o'clock").
     on wallclock time) timers.
     AnyEvent always prefers relative timers, if available, matching the
     AnyEvent API.
+    AnyEvent has two additional methods that return the "current time":
+    AnyEvent->time
+        This returns the "current wallclock time" as a fractional number of
+        seconds since the Epoch (the same thing as "time" or
+        "Time::HiRes::time" return, and the result is guaranteed to be
+        compatible with those).
+        It progresses independently of any event loop processing, i.e. each
+        call will check the system clock, which usually gets updated
+        frequently.
+    AnyEvent->now
+        This also returns the "current wallclock time", but unlike "time",
+        above, this value might change only once per event loop iteration,
+        depending on the event loop (most return the same time as "time",
+        above). This is the time that AnyEvent's timers get scheduled
+        against.
+        *In almost all cases (in all cases if you don't care), this is the
+        function to call when you want to know the current time.*
+        This function is also often faster then "AnyEvent->time", and thus
+        the preferred method if you want some timestamp (for example,
+        AnyEvent::Handle uses this to update it's activity timeouts).
+        The rest of this section is only of relevance if you try to be very
+        exact with your timing, you can skip it without bad conscience.
+        For a practical example of when these times differ, consider
+        Event::Lib and EV and the following set-up:
+        The event loop is running and has just invoked one of your callback
+        at time=500 (assume no other callbacks delay processing). In your
+        callback, you wait a second by executing "sleep 1" (blocking the
+        process for a second) and then (at time=501) you create a relative
+        timer that fires after three seconds.
+        With Event::Lib, "AnyEvent->time" and "AnyEvent->now" will both
+        return 501, because that is the current time, and the timer will be
+        scheduled to fire at time=504 (501 + 3).
+        With EV, "AnyEvent->time" returns 501 (as that is the current time),
+        but "AnyEvent->now" returns 500, as that is the time the last event
+        processing phase started. With EV, your timer gets scheduled to run
+        at time=503 (500 + 3).
+        In one sense, Event::Lib is more exact, as it uses the current time
+        regardless of any delays introduced by event processing. However,
+        most callbacks do not expect large delays in processing, so this
+        causes a higher drift (and a lot more system calls to get the
+        current time).
+        In another sense, EV is more exact, as your timer will be scheduled
+        at the same time, regardless of how long event processing actually
+        took.
+        In either case, if you care (and in most cases, you don't), then you
+        can get whatever behaviour you want with any event loop, by taking
+        the difference between "AnyEvent->time" and "AnyEvent->now" into
+        account.
   SIGNAL WATCHERS
     You can watch for signals using a signal watcher, "signal" is the signal
-    *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked
+    *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
-    whenever a signal occurs.
+    callback to be invoked whenever a signal occurs.
     Although the callback might get passed parameters, their value and
     presence is undefined and you cannot rely on them. Portable AnyEvent
     callbacks cannot use arguments passed to signal watcher callbacks.
-    Multiple signal occurances can be clumped together into one callback
+    Multiple signal occurrences can be clumped together into one callback
-    invocation, and callback invocation will be synchronous. synchronous
+    invocation, and callback invocation will be synchronous. Synchronous
     means that it might take a while until the signal gets handled by the
-    process, but it is guarenteed not to interrupt any other callbacks.
+    process, but it is guaranteed not to interrupt any other callbacks.
     The main advantage of using these watchers is that you can share a
     signal between multiple watchers.
     This watcher might use %SIG, so programs overwriting those signals
     an AnyEvent program, you *have* to create at least one watcher before
     you "fork" the child (alternatively, you can call "AnyEvent::detect").
     Example: fork a process and wait for it
-      my $done = AnyEvent->condvar;
+       my $done = AnyEvent->condvar;
-      my $pid = fork or exit 5;
+   my $pid = fork or exit 5;
-      my $w = AnyEvent->child (
+   my $w = AnyEvent->child (
-         pid => $pid,
+          pid => $pid,
-         cb  => sub {
+          cb  => sub {
-            my ($pid, $status) = @_;
+             my ($pid, $status) = @_;
-            warn "pid $pid exited with status $status";
+             warn "pid $pid exited with status $status";
-            $done->send;
+             $done->send;
-         },
+          },
-      );
+       );
-      # do something else, then wait for process exit
+   # do something else, then wait for process exit
-      $done->recv;
+       $done->recv;
   CONDITION VARIABLES
     If you are familiar with some event loops you will know that all of them
     require you to run some blocking "loop", "run" or similar function that
     will actively watch for new events and call your callbacks.
     The instrument to do that is called a "condition variable", so called
     because they represent a condition that must become true.
     Condition variables can be created by calling the "AnyEvent->condvar"
     method, usually without arguments. The only argument pair allowed is
     "cb", which specifies a callback to be called when the condition
-    variable becomes true.
+    variable becomes true, with the condition variable as the first argument
+    (but not the results).
-    After creation, the conditon variable is "false" until it becomes "true"
+    After creation, the condition variable is "false" until it becomes
+    "true" by calling the "send" method (or calling the condition variable
+    as if it were a callback, read about the caveats in the description for
-    by calling the "send" method.
+    the "->send" method).
     Condition variables are similar to callbacks, except that you can
     optionally wait for them. They can also be called merge points - points
-    in time where multiple outstandign events have been processed. And yet
+    in time where multiple outstanding events have been processed. And yet
-    another way to call them is transations - each condition variable can be
+    another way to call them is transactions - each condition variable can
-    used to represent a transaction, which finishes at some point and
+    be used to represent a transaction, which finishes at some point and
     delivers a result.
     Condition variables are very useful to signal that something has
     finished, for example, if you write a module that does asynchronous http
     requests, then a condition variable would be the ideal candidate to
     you can block your main program until an event occurs - for example, you
     could "->recv" in your main program until the user clicks the Quit
     button of your app, which would "->send" the "quit" event.
     Note that condition variables recurse into the event loop - if you have
-    two pieces of code that call "->recv" in a round-robbin fashion, you
+    two pieces of code that call "->recv" in a round-robin fashion, you
     lose. Therefore, condition variables are good to export to your caller,
     but you should avoid making a blocking wait yourself, at least in
     callbacks, as this asks for trouble.
     Condition variables are represented by hash refs in perl, and the keys
     There are two "sides" to a condition variable - the "producer side"
     which eventually calls "-> send", and the "consumer side", which waits
     for the send to occur.
-    Example:
+    Example: wait for a timer.
        # wait till the result is ready
        my $result_ready = AnyEvent->condvar;
        # do something such as adding a timer
        # this "blocks" (while handling events) till the callback
        # calls send
        $result_ready->recv;
+    Example: wait for a timer, but take advantage of the fact that condition
+    variables are also code references.
+       my $done = AnyEvent->condvar;
+       my $delay = AnyEvent->timer (after => 5, cb => $done);
+       $done->recv;
+    Example: Imagine an API that returns a condvar and doesn't support
+    callbacks. This is how you make a synchronous call, for example from the
+    main program:
+       use AnyEvent::CouchDB;
+       ...
+       my @info = $couchdb->info->recv;
+    And this is how you would just ste a callback to be called whenever the
+    results are available:
+       $couchdb->info->cb (sub {
+          my @info = $_[0]->recv;
+       });
    METHODS FOR PRODUCERS
     These methods should only be used by the producing side, i.e. the
     code/module that eventually sends the signal. Note that it is also the
     producer side which creates the condvar in most cases, but it isn't
     uncommon for the consumer to create it as well.
         If a callback has been set on the condition variable, it is called
         immediately from within send.
         Any arguments passed to the "send" call will be returned by all
         future "->recv" calls.
+        Condition variables are overloaded so one can call them directly (as
+        a code reference). Calling them directly is the same as calling
+        "send". Note, however, that many C-based event loops do not handle
+        overloading, so as tempting as it may be, passing a condition
+        variable instead of a callback does not work. Both the pure perl and
+        EV loops support overloading, however, as well as all functions that
+        use perl to invoke a callback (as in AnyEvent::Socket and
+        AnyEvent::DNS for example).
     $cv->croak ($error)
         Similar to send, but causes all call's to "->recv" to invoke
         "Carp::croak" with the given error message/object/scalar.
         (the loop doesn't execute once).
         This is the general pattern when you "fan out" into multiple
         subrequests: use an outer "begin"/"end" pair to set the callback and
         ensure "end" is called at least once, and then, for each subrequest
-        you start, call "begin" and for eahc subrequest you finish, call
+        you start, call "begin" and for each subrequest you finish, call
         "end".
    METHODS FOR CONSUMERS
     These methods should only be used by the consuming side, i.e. the code
     awaits the condition.
         (programs might want to do that to stay interactive), so *if you are
         using this from a module, never require a blocking wait*, but let
         the caller decide whether the call will block or not (for example,
         by coupling condition variables with some kind of request results
         and supporting callbacks so the caller knows that getting the result
-        will not block, while still suppporting blocking waits if the caller
+        will not block, while still supporting blocking waits if the caller
         so desires).
         Another reason *never* to "->recv" in a module is that you cannot
         sensibly have two "->recv"'s in parallel, as that would require
         multiple interpreters or coroutines/threads, none of which
     $bool = $cv->ready
         Returns true when the condition is "true", i.e. whether "send" or
         "croak" have been called.
-    $cb = $cv->cb ([new callback])
+    $cb = $cv->cb ($cb->($cv))
         This is a mutator function that returns the callback set and
         optionally replaces it before doing so.
         The callback will be called when the condition becomes "true", i.e.
-        when "send" or "croak" are called. Calling "recv" inside the
+        when "send" or "croak" are called, with the only argument being the
+        condition variable itself. Calling "recv" inside the callback or at
-        callback or at any later time is guaranteed not to block.
+        any later time is guaranteed not to block.
 GLOBAL VARIABLES AND FUNCTIONS
     $AnyEvent::MODEL
         Contains "undef" until the first watcher is being created. Then it
         contains the event model that is being used, which is the name of
     If it doesn't care, it can just "use AnyEvent" and use it itself, or not
     do anything special (it does not need to be event-based) and let
     AnyEvent decide which implementation to chose if some module relies on
     it.
-    If the main program relies on a specific event model. For example, in
+    If the main program relies on a specific event model - for example, in
-    Gtk2 programs you have to rely on the Glib module. You should load the
+    Gtk2 programs you have to rely on the Glib module - you should load the
     event module before loading AnyEvent or any module that uses it:
     generally speaking, you should load it as early as possible. The reason
     is that modules might create watchers when they are loaded, and AnyEvent
     will decide on the event model to use as soon as it creates watchers,
     and it might chose the wrong one unless you load the correct one
     yourself.
-    You can chose to use a rather inefficient pure-perl implementation by
+    You can chose to use a pure-perl implementation by loading the
-    loading the "AnyEvent::Impl::Perl" module, which gives you similar
+    "AnyEvent::Impl::Perl" module, which gives you similar behaviour
-    behaviour everywhere, but letting AnyEvent chose is generally better.
+    everywhere, but letting AnyEvent chose the model is generally better.
+  MAINLOOP EMULATION
+    Sometimes (often for short test scripts, or even standalone programs who
+    only want to use AnyEvent), you do not want to run a specific event
+    loop.
+    In that case, you can use a condition variable like this:
+       AnyEvent->condvar->recv;
+    This has the effect of entering the event loop and looping forever.
+    Note that usually your program has some exit condition, in which case it
+    is better to use the "traditional" approach of storing a condition
+    variable somewhere, waiting for it, and sending it when the program
+    should exit cleanly.
 OTHER MODULES
     The following is a non-exhaustive list of additional modules that use
     AnyEvent and can therefore be mixed easily with other AnyEvent modules
     in the same program. Some of the modules come with AnyEvent, some are
     AnyEvent::Util
         Contains various utility functions that replace often-used but
         blocking functions such as "inet_aton" by event-/callback-based
         versions.
+    AnyEvent::Socket
+        Provides various utility functions for (internet protocol) sockets,
+        addresses and name resolution. Also functions to create non-blocking
+        tcp connections or tcp servers, with IPv6 and SRV record support and
+        more.
     AnyEvent::Handle
-        Provide read and write buffers and manages watchers for reads and
+        Provide read and write buffers, manages watchers for reads and
-        writes.
+        writes, supports raw and formatted I/O, I/O queued and fully
+        transparent and non-blocking SSL/TLS.
+    AnyEvent::DNS
+        Provides rich asynchronous DNS resolver capabilities.
+    AnyEvent::HTTP
+        A simple-to-use HTTP library that is capable of making a lot of
+        concurrent HTTP requests.
     AnyEvent::HTTPD
         Provides a simple web application server framework.
-    AnyEvent::DNS
-        Provides asynchronous DNS resolver capabilities, beyond what
-        AnyEvent::Util offers.
     AnyEvent::FastPing
         The fastest ping in the west.
+    AnyEvent::DBI
+        Executes DBI requests asynchronously in a proxy process.
+    AnyEvent::AIO
+        Truly asynchronous I/O, should be in the toolbox of every event
+        programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
+        together.
+    AnyEvent::BDB
+        Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
+        fuses BDB and AnyEvent together.
+    AnyEvent::GPSD
+        A non-blocking interface to gpsd, a daemon delivering GPS
+        information.
+    AnyEvent::IGS
+        A non-blocking interface to the Internet Go Server protocol (used by
+        App::IGS).
     Net::IRC3
         AnyEvent based IRC client module family.
     Net::XMPP2
     Event::ExecFlow
         High level API for event-based execution flow control.
     Coro
         Has special support for AnyEvent via Coro::AnyEvent.
-    AnyEvent::AIO, IO::AIO
-        Truly asynchronous I/O, should be in the toolbox of every event
-        programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
-        together.
-    AnyEvent::BDB, BDB
-        Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently
-        fuses IO::AIO and AnyEvent together.
     IO::Lambda
         The lambda approach to I/O - don't ask, look there. Can use
         AnyEvent.
         by "PERL_ANYEVENT_MODEL".
         When set to 2 or higher, cause AnyEvent to report to STDERR which
         event model it chooses.
+    "PERL_ANYEVENT_STRICT"
+        AnyEvent does not do much argument checking by default, as thorough
+        argument checking is very costly. Setting this variable to a true
+        value will cause AnyEvent to load "AnyEvent::Strict" and then to
+        thoroughly check the arguments passed to most method calls. If it
+        finds any problems it will croak.
+        In other words, enables "strict" mode.
+        Unlike "use strict" it is definitely recommended ot keep it off in
+        production.
     "PERL_ANYEVENT_MODEL"
         This can be used to specify the event model to be used by AnyEvent,
-        before autodetection and -probing kicks in. It must be a string
+        before auto detection and -probing kicks in. It must be a string
         consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
         gets prepended and the resulting module name is loaded and if the
         load was successful, used as event model. If it fails to load
-        AnyEvent will proceed with autodetection and -probing.
+        AnyEvent will proceed with auto detection and -probing.
         This functionality might change in future versions.
         For example, to force the pure perl model (AnyEvent::Impl::Perl) you
         could start your program like this:
-          PERL_ANYEVENT_MODEL=Perl perl ...
+           PERL_ANYEVENT_MODEL=Perl perl ...
+    "PERL_ANYEVENT_PROTOCOLS"
+        Used by both AnyEvent::DNS and AnyEvent::Socket to determine
+        preferences for IPv4 or IPv6. The default is unspecified (and might
+        change, or be the result of auto probing).
+        Must be set to a comma-separated list of protocols or address
+        families, current supported: "ipv4" and "ipv6". Only protocols
+        mentioned will be used, and preference will be given to protocols
+        mentioned earlier in the list.
+        This variable can effectively be used for denial-of-service attacks
+        against local programs (e.g. when setuid), although the impact is
+        likely small, as the program has to handle connection errors
+        already-
+        Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over
+        IPv6, but support both and try to use both.
+        "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to
+        resolve or contact IPv6 addresses.
+        "PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4" support either IPv4 or IPv6, but
+        prefer IPv6 over IPv4.
+    "PERL_ANYEVENT_EDNS0"
+        Used by AnyEvent::DNS to decide whether to use the EDNS0 extension
+        for DNS. This extension is generally useful to reduce DNS traffic,
+        but some (broken) firewalls drop such DNS packets, which is why it
+        is off by default.
+        Setting this variable to 1 will cause AnyEvent::DNS to announce
+        EDNS0 in its DNS requests.
+    "PERL_ANYEVENT_MAX_FORKS"
+        The maximum number of child processes that
+        "AnyEvent::Util::fork_call" will create in parallel.
 EXAMPLE PROGRAM
     The following program uses an I/O watcher to read data from STDIN, a
     timer to display a message once per second, and a condition variable to
     quit the program when the user enters quit:
           poll => 'r',
           cb   => sub {
              warn "io event <$_[0]>\n";   # will always output <r>
              chomp (my $input = <STDIN>); # read a line
              warn "read: $input\n";       # output what has been read
-             $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
+             $cv->send if $input =~ /^q/i; # quit program if /^q/i
           },
        );
        my $time_watcher; # can only be used once
           });
        }
        new_timer; # create first timer
-       $cv->wait; # wait until user enters /^q/i
+       $cv->recv; # wait until user enters /^q/i
 REAL-WORLD EXAMPLE
     Consider the Net::FCP module. It features (among others) the following
     API calls, which are to freenet what HTTP GET requests are to http:
        syswrite $txn->{fh}, $txn->{request}
           or die "connection or write error";
        $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
     Again, "fh_ready_r" waits till all data has arrived, and then stores the
-    result and signals any possible waiters that the request ahs finished:
+    result and signals any possible waiters that the request has finished:
        sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
        if (end-of-file or data complete) {
          $txn->{result} = $txn->{buf};
-         $txn->{finished}->broadcast;
+         $txn->{finished}->send;
          $txb->{cb}->($txn) of $txn->{cb}; # also call callback
        }
     The "result" method, finally, just waits for the finished signal (if the
     request was already finished, it doesn't wait, of course, and returns
     the data:
-       $txn->{finished}->wait;
+       $txn->{finished}->recv;
        return $txn->{result};
     The actual code goes further and collects all errors ("die"s,
-    exceptions) that occured during request processing. The "result" method
+    exceptions) that occurred during request processing. The "result" method
     detects whether an exception as thrown (it is stored inside the $txn
     object) and just throws the exception, which means connection errors and
     other problems get reported tot he code that tries to use the result,
     not in a random callback.
        my $quit = AnyEvent->condvar;
        $fcp->txn_client_get ($url)->cb (sub {
           ...
-          $quit->broadcast;
+          $quit->send;
        });
-       $quit->wait;
+       $quit->recv;
 BENCHMARKS
     To give you an idea of the performance and overheads that AnyEvent adds
     over the event loops themselves and to give you an impression of the
     speed of various event loops I prepared some benchmarks.
   BENCHMARKING ANYEVENT OVERHEAD
     Here is a benchmark of various supported event models used natively and
-    through anyevent. The benchmark creates a lot of timers (with a zero
+    through AnyEvent. The benchmark creates a lot of timers (with a zero
     timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
     which it is), lets them fire exactly once and destroys them again.
     Source code for this benchmark is found as eg/bench in the AnyEvent
     distribution.
     between all watchers, to avoid adding memory overhead. That means
     closure creation and memory usage is not included in the figures.
     *invoke* is the time, in microseconds, used to invoke a simple callback.
     The callback simply counts down a Perl variable and after it was invoked
-    "watcher" times, it would "->broadcast" a condvar once to signal the end
+    "watcher" times, it would "->send" a condvar once to signal the end of
-    of this phase.
+    this phase.
     *destroy* is the time, in microseconds, that it takes to destroy a
     single watcher.
    Results
     *   You should avoid POE like the plague if you want performance or
         reasonable memory usage.
   BENCHMARKING THE LARGE SERVER CASE
-    This benchmark atcually benchmarks the event loop itself. It works by
+    This benchmark actually benchmarks the event loop itself. It works by
-    creating a number of "servers": each server consists of a socketpair, a
+    creating a number of "servers": each server consists of a socket pair, a
     timeout watcher that gets reset on activity (but never fires), and an
     I/O watcher waiting for input on one side of the socket. Each time the
     socket watcher reads a byte it will write that byte to a random other
     "server".
     The effect is that there will be a lot of I/O watchers, only part of
     which are active at any one point (so there is a constant number of
-    active fds for each loop iterstaion, but which fds these are is random).
+    active fds for each loop iteration, but which fds these are is random).
     The timeout is reset each time something is read because that reflects
     how most timeouts work (and puts extra pressure on the event loops).
-    In this benchmark, we use 10000 socketpairs (20000 sockets), of which
+    In this benchmark, we use 10000 socket pairs (20000 sockets), of which
     100 (1%) are active. This mirrors the activity of large servers with
     many connections, most of which are idle at any one point in time.
     Source code for this benchmark is found as eg/bench2 in the AnyEvent
     distribution.
    Explanation of the columns
     *sockets* is the number of sockets, and twice the number of "servers"
     (as each server has a read and write socket end).
-    *create* is the time it takes to create a socketpair (which is
+    *create* is the time it takes to create a socket pair (which is
     nontrivial) and two watchers: an I/O watcher and a timeout watcher.
     *request*, the most important value, is the time it takes to handle a
     single "request", that is, reading the token from the pipe and
     forwarding it to another server. This includes deleting the old timeout
     and speed most when you have lots of watchers, not when you only have a
     few of them).
     EV is again fastest.
-    Perl again comes second. It is noticably faster than the C-based event
+    Perl again comes second. It is noticeably faster than the C-based event
     loops Event and Glib, although the difference is too small to really
     matter.
     POE also performs much better in this case, but is is still far behind
     the others.
     model than specified in the variable.
     You can make AnyEvent completely ignore this variable by deleting it
     before the first watcher gets created, e.g. with a "BEGIN" block:
-      BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
+       BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
-      use AnyEvent;
+   use AnyEvent;
     Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
     be used to probe what backend is used and gain other information (which
-    is probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
+    is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
+    and $ENV{PERL_ANYEGENT_STRICT}.
+BUGS
+    Perl 5.8 has numerous memleaks that sometimes hit this module and are
+    hard to work around. If you suffer from memleaks, first upgrade to Perl
+    5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
+    annoying mamleaks, such as leaking on "map" and "grep" but it is usually
+    not as pronounced).
 SEE ALSO
+    Utility functions: AnyEvent::Util.
     Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
     Event::Lib, Qt, POE.
     Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
     AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
     AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.
+    Non-blocking file handles, sockets, TCP clients and servers:
+    AnyEvent::Handle, AnyEvent::Socket.
+    Asynchronous DNS: AnyEvent::DNS.
     Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
-    Nontrivial usage examples: Net::FCP, Net::XMPP2.
+    Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.
 AUTHOR
-     Marc Lehmann <schmorp@schmorp.de>
+       Marc Lehmann <schmorp@schmorp.de>
-     http://home.schmorp.de/
+       http://home.schmorp.de/

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Revision 1.29 by root, Tue Jul 29 10:20:33 2008 UTC